Aggregation of biodegradable amphiphilic poly(succinimide-co-N-propyl aspartamide) and poly(N-dodecyl aspartamide-co-N-propyl aspartamide) in aqueous medium and its preliminary drug-released properties

Two series of biodegradable amphiphilic copolymers, poly(succinimide-co-N-propyl aspartamide) (PSI-PA) and poly(N-dodecyl aspartamide-co-N-propyl aspartamide) (PDDA-PA) were synthesized by partial and total aminolysis of polysuccinimide (PSI), respectively. PSI-PA copolymers could self-aggregate in water directly under ultrasonication at room temperature. Differing from PSI-PA copolymers, the aggregates of PDDA-PA need to add PDDA-PA DMF solution into an excessive amount of water. The aggregative properties of PSI-PA and PDDA-PA copolymers have been investigated by dynamic light scattering (DLS) and surface tension measurements. Hydrophilicity of these two copolymers was attributed to the N-propyl aspartamide segments. Due to the stiff structure, succinimide segments preferred to form irregular hydrophobic microdomains, and some aggregates of PSI-PA are bimodal size distribution in water medium, while the more flexible PDDA-PA copolymer chains preferred to form monodispersed spherical aggregates. Elevated temperature could reduce the aggregate size of both PSI-PA and PDDA-PA copolymers due to the breaking of the hydrogen bonding and the releasing of the bonded water molecules. PSI-PA copolymers were surface active, while the surface tension of PDDA-PA copolymers was independent on concentration. The drug-loaded aggregates of PSI-PA also have been prepared and the preliminary release properties have been studied in vitro.